Pathotypes of Globodera spp. as detected by superoxide dismutase iso-electrofocusing patterns

Twelve populations of Globodera rostochiensis and 3 populations of G. pallida were collected from different States of Venezuela, and different Chilean and Italian regions. Standards of Ro1, Ro2, Ro3, Ro4, Ro5 pathotypes of G. rostochiensis, and of Pa2, Pa3 pathotypes of G. pallida were provided by the Czech University of Life Sciences in Prague. About one hundred cysts of each population were used to extract proteins. Proteins were separated according to their charge by isoelectrofocusing (IEF) on mini-gels inserted into the automated Phast-System® equipment. Gels were stained for superoxide dismutase (SOD) activity. A high SOD polymorphism was found among the tested samples with the presence of up to 12 enzyme activity main bands at different isoelectric point (pI range 8.7-4.4). By means of a matrix built up on the presence/absence of these 12 bands, considered as variables, a cluster analysis was carried out and a UPGMA dendogram was obtained. Groups including populations of the 2 different species were well discerned by this analysis, as predicted. Interestingly, the group including Ro1 standard was markedly distant from those including all the other G. rostochiensis populations and standards. Ro2, Ro4, Ro5 standards grouped together in a cluster different from that including Ro3. However, Ro2 belongs to a subgroup which can still be differentiated from that to which Ro4 and Ro5 belong. The provided standards of these latter pathotypes actually show almost identical IEF patterns. Standards of Pa2 and Pa3 pathotypes were easily differentiated by this analysis. Also if this method may be improved by using IEF patterns from other enzymes, this study indicates that isozyme IEF phenotypes may be utilized to identify pathotypes or virulence groups of these cyst nematodes in a manner easier, faster and more economic than that using the differential Solanum clones.